using System; 
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.Common; 
using System.Data.SqlClient;
using System.Linq.Expressions; 
using System.IO; 
using System.Reflection;
using System.Text; 
using System.Transactions;

namespace System.Data.Linq.SqlClient {
    using System.Data.Linq; 
    using System.Data.Linq.Provider;
 
    internal class SqlConnectionManager : IConnectionManager { 
        private IProvider provider;
        private DbConnection connection; 
        private bool autoClose;
        private bool disposeConnection;  // should we dispose this connection when the context is disposed?
        private DbTransaction transaction;
        private Transaction systemTransaction; 
        private SqlInfoMessageEventHandler infoMessagehandler;
        private List<IConnectionUser> users; 
        private int maxUsers; 

        internal SqlConnectionManager(IProvider provider, DbConnection con, int maxUsers, bool disposeConnection) { 
            this.provider = provider;
            this.connection = con;
            this.maxUsers = maxUsers;
            this.infoMessagehandler = new SqlInfoMessageEventHandler(this.OnInfoMessage); 
            this.users = new List<IConnectionUser>(maxUsers);
            this.disposeConnection = disposeConnection; 
        } 

 
        public DbConnection UseConnection(IConnectionUser user) {
            if (user == null) {
                throw Error.ArgumentNull("user");
            } 
            if (this.connection.State == ConnectionState.Closed) {
                this.connection.Open(); 
                this.autoClose = true; 
                this.AddInfoMessageHandler();
                if (System.Transactions.Transaction.Current != null) { 
                    System.Transactions.Transaction.Current.TransactionCompleted += this.OnTransactionCompleted;
                }
            }
            if (this.transaction == null && System.Transactions.Transaction.Current != null && 
                        System.Transactions.Transaction.Current != systemTransaction) {
                this.ClearConnection(); 
                systemTransaction = System.Transactions.Transaction.Current; 
                this.connection.EnlistTransaction(System.Transactions.Transaction.Current);
            } 

            if (this.users.Count == this.maxUsers) {
                this.BootUser(this.users[0]);
            } 
            this.users.Add(user);
            return this.connection; 
        } 

        private void BootUser(IConnectionUser user) { 
            bool saveAutoClose = this.autoClose;
            this.autoClose = false;
            int index = this.users.IndexOf(user);
            if (index >= 0) { 
                this.users.RemoveAt(index);
            } 
            user.CompleteUse(); 
            this.autoClose = saveAutoClose;
        } 

        internal DbConnection Connection {
            get { return this.connection; }
        } 

        internal int MaxUsers { 
            get { return this.maxUsers; } 
        }
 
        internal void DisposeConnection() {
            // only close this guy if we opened it in the first place
            if (this.autoClose) {
                this.CloseConnection(); 
            }
 
            // If we created the connection, we need to dispose it even if the user explicitly 
            // opened it using the Connection property on the context.
            if (this.connection != null && this.disposeConnection) { 
                this.connection.Dispose();
                this.connection = null;
            }
        } 

        internal void ClearConnection() { 
            while (this.users.Count > 0) { 
                this.BootUser(this.users[0]);
            } 
        }

        internal bool AutoClose {
            get { return this.autoClose; } 
            set { this.autoClose = value; }
        } 
 
        internal DbTransaction Transaction {
            get { return this.transaction; } 
            set {
                if (value != this.transaction) {
                    if (value != null) {
                        if (this.connection != value.Connection) { 
                            throw Error.TransactionDoesNotMatchConnection();
                        } 
                    } 
                    this.transaction = value;
                } 
            }
        }

        public void ReleaseConnection(IConnectionUser user) { 
            if (user == null) {
                throw Error.ArgumentNull("user"); 
            } 
            int index = this.users.IndexOf(user);
            if (index >= 0) { 
                this.users.RemoveAt(index);
            }
            if (this.users.Count == 0 && this.autoClose && this.transaction == null && System.Transactions.Transaction.Current == null) {
                this.CloseConnection(); 
            }
        } 
 
        private void CloseConnection() {
            if (this.connection != null && this.connection.State != ConnectionState.Closed) { 
                this.connection.Close();
            }
            this.RemoveInfoMessageHandler();
            this.autoClose = false; 
        }
 
        private void OnInfoMessage(object sender, SqlInfoMessageEventArgs args) { 
            if (this.provider.Log != null) {
                this.provider.Log.WriteLine(string.Format(Strings.LogGeneralInfoMessage,args.Source, args.Message)); 
            }
        }

        private void OnTransactionCompleted(object sender, System.Transactions.TransactionEventArgs args) { 
            if (this.users.Count == 0 && this.autoClose) {
                this.CloseConnection(); 
            } 
        }
 
        private void AddInfoMessageHandler() {
            SqlConnection scon = this.connection as SqlConnection;
            if (scon != null) {
                scon.InfoMessage += this.infoMessagehandler; 
            }
        } 
 
        private void RemoveInfoMessageHandler() {
            SqlConnection scon = this.connection as SqlConnection; 
            if (scon != null) {
                scon.InfoMessage -= this.infoMessagehandler;
            }
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.